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Auxiliary material for paper 2011GL050546
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A New Approach for Estimating Entrainment Rate in Cumulus
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Clouds
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Chunsong Lu1, 2, Yangang Liu2, Seong Soo Yum3, Shengjie Niu1, Satoshi Endo2
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1. School of Atmospheric Physics, Key Laboratory of Meteorological Disaster of
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Ministry of Education, Nanjing University of Information Science and Technology
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(NUIST), Jiangsu, China 210044
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2. Atmospheric Sciences Division, Brookhaven National Laboratory (BNL), NY
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11973
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3. Department of Atmospheric Sciences, Yonsei University, Seoul 120-749, Korea
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To complement the validation of the new approach with observation in the full
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article, we apply the new approach and the traditional approach to a continental
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cumulus case simulated by a large eddy simulation (LES) model [see Endo et al.,
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2011 about the details of the LES model]. The simulated cloud is a benchmark case
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based on the sounding and surface flux observations on 21 June 1997 at the
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Atmospheric Radiation Measurement Southern Great Plains site [Brown et al., 2002].
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We estimated entrainment rate profile in the cumulus cloud core from the model
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results at every minute during 1200-1300 LST and then obtain the average
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entrainment rate profile; cloud core is defined with positive buoyancy (virtual
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potential temperature in the cloud is larger than that in the environment) and liquid
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water mixing ratio > 0.01 g kg-1. The cloud base height is defined as the height of the
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lowest cloud grid point; the temperature, water vapor mixing ratio profiles in the
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cloud and the environment, and liquid water mixing ratio profile in the cloud can be
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determined. The traditional approach is applied to two conserved properties, total
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water mixing ratio (qt) and liquid water potential temperature (θl), separately. The
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results obtained using the different approaches are compared in Figure S1. It is
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interesting to note that the traditional approach with total water mixing ratio and
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liquid water potential temperature as the two conserved variables produces
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systematically different entrainment rates while the entrainment rates estimated from
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the new approach lie between those estimated from the traditional approach. This
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further gives us more confidence in our new approach. Neggers et al. [2003] reported
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and discussed similar differences between the entrainment rates estimated using the
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same traditional approach with total water mixing ratio and liquid water potential
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temperature as the conserved variables.
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Figure S1. the entrainment rates estimated from the traditional approach with
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conserved properties: total water mixing ratio (qt) and liquid water potential
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temperature (θl), respectively, and from the new approach.
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References:
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Brown, A. R., R. T. Cederwall, A. Chlond, P. G. Duynkerke, J. C. Golaz, M.
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Khairoutdinov, D. C. Lewellen, A. P. Lock, M. K. MacVean, C. H. Moeng, R. A. J.
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Endo, S., Y. Liu, W. Lin, and G. Liu (2011), Extension of WRF to cloud-resolving
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simulations driven by large-scale and surface forcings, Monthly Weather Review,
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(submitted).
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Neggers, R. A. J., P. G. Duynkerke, and S. M. A. Rodts (2003), Shallow cumulus
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convection: A validation of large-eddy simulation against aircraft and Landsat
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observations, Q. J. Roy. Meteor. Soc., 129(593), 2671-2696, doi:10.1256/qj.02.93.